1. Technical Field
The present invention relates to an image display apparatus.
2. Related Art
Heretofore, an image display apparatus which synthesizes R (red), G (green), and B (blue) color lights modulated by three optical modulation devices each having a liquid crystal panel, and the like, using a color synthesis optical device, and projects the synthesized color light onto a screen, allowing an observer to view a projection image on the screen stereoscopically, has been known (for example, refer to JP-A-2001-174750).
With the image display apparatus described in JP-A-2001-174750, the three optical modulation devices carry out an alternate switching between a first period in which a left eye image light is formed and a second period in which a right eye image light is formed.
Also, with the image display apparatus, a polarizing filter or the like is provided on the optical path downstream side of the color synthesis optical device, whereby each image light emitted from the color synthesis optical device is converted into a predetermined polarization condition in the first period, and converted into a polarization condition differing from the predetermined polarization condition in the second period.
Then, the observer views the projection image stereoscopically by visually perceiving only each image light (left eye image light) in the predetermined polarization condition with the left eye, and visually perceiving each image light (right eye image light) in the polarization condition differing from the predetermined polarization condition with the right eye, through polarized glasses.
Meanwhile, a technology which, to synthesize each color light in a color synthesis optical device, controls a loss of the quantity of each color light utilizing the characteristics of an S polarized light and P polarized light has also been known (for example, refer to JP-A-2005-43913).
With the technology described in JP-A-2005-43913, a configuration is such that a G color light enters as the P polarized light, and each of R and B color lights enters as the S polarized light, on a pair of dielectric multilayer films crossing in an approximate X-shape in the color synthesis optical device.
That is, as the G color light enters on the pair of dielectric multilayer films as the P polarized light, it is effectively transmitted through the pair of dielectric multilayer films, reducing the loss of the light quantity. Meanwhile, as each of the R and B color lights enters on the pair of dielectric multilayer films as the S polarized light, it is effectively reflected by the pair of dielectric multilayer films, reducing the loss of the light quantity.
However, the image display apparatus described in JP-A-2001-174750 is configured on the assumption that the image lights emitted from the three optical modulation devices are of the same linear polarization.
For this reason, when the technology described in JP-A-2005-43913 is applied to the image display apparatus described in JP-A-2001-174750, the following problem will arise.
That is, as the image light emitted from one optical modulation device, among the three optical modulation devices, and the image light emitted from another optical modulation device are linearly polarized lights whose polarization directions are perpendicular to each other, even by converting the polarization conditions with the polarizing filter or the like, it is not possible to convert all the polarization conditions into the same polarization condition.
For example, in the first period, the left eye image light emitted from one optical modulation device is converted into the predetermined polarization condition, and the left eye image light emitted from another optical modulation device is converted into the polarization condition differing from the predetermined polarization condition, by the polarizing filter or the like. For this reason, in the first period, the observer, while visually perceiving the left eye image light emitted from the one optical modulation device with the left eye, visually perceives the left eye image light emitted from the other optical modulation device with the right eye, through the polarized glasses. The same also applies in the second period.